JP2005038561A - Magnetic tape cartridge, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic tape cartridge capable of enhancing the durability of a clamping member for fastening and holding a leader pin at one end of a magnetic tape thereby securing its reliability and to provide a method for manufacturing the magnetic tape cartridge. <P>SOLUTION: The clamping member consists of an injection molding of a synthetic resin material having an internal cavity 55 which houses a leader pin shank and an aperture groove 56 which is formed at a transverse size smaller than that of the leader pin shank and communicates with the internal cavity 55 over the entire area of its axial direction. Its gate trace G 1 is formed on the inner wall surface of the aperture groove 56 of the clamping member 52A in such a manner that the flow direction of the synthetic resin material intersects with a region 58 having an opposing relation with the forming region of the aperture groove 56 across the internal cavity 55. Also, an enlarged part of a flow passage is constituted by a flat surface 55a formed on the inside surface side of the region 58. As a result, the reliability of the magnetic tape cartridge can be assured and the productivity can be improved by preventing the occurrence of the crack of the clamping member 52A. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetic tape cartridge provided with a leader pin for pulling out a tape at one end of the magnetic tape and a method for manufacturing the same, and more particularly, to improve the durability of a clamp member that holds the leader pin firmly to one end of the magnetic tape. The present invention relates to a magnetic tape cartridge and a manufacturing method thereof.

  Conventionally, a magnetic tape cartridge used as a recording medium used in an external storage device such as a computer is of a type in which a magnetic tape is wound around a single reel and the reel is rotatably accommodated in the cartridge body. Things are generally known. This type of magnetic tape cartridge is used for storing data in a computer or the like, and is required to have high reliability because important and enormous information is recorded.

  In a single reel type magnetic tape cartridge, in order to write / read information to / from the magnetic tape, the magnetic tape can be easily pulled out to a take-up reel provided on the tape drive device side. A member is attached to one end of the magnetic tape. When the cartridge is not in use, the member is anchored at a predetermined position by anchoring members provided on the inner surface of the upper wall and the inner surface of the bottom wall of the cartridge body. Further, when the tape drive device side pulls out the magnetic tape, the magnetic tape can be easily and properly pulled out by being moored at a predetermined position.

  For example, in an LTO format (linear tape open format) magnetic tape cartridge, a member attached to one end of the magnetic tape corresponds to a leader pin, and a member that anchors it at a predetermined position of the cartridge body serves as an elastic holder. Will respond. A clamp member is used to securely hold the leader pin to one end of the magnetic tape.

  As shown in FIG. 10, this type of clamping member 10 is formed with an internal space 11 that accommodates the shaft portion of the leader pin and a width that is smaller than the shaft diameter of the shaft portion of the leader pin. On the other hand, it is composed of an injection molded body of a synthetic resin material having a C-shaped cross section having an opening groove 12 communicating over the entire axial direction (see Patent Document 1 below).

  In the clamp member 10 having such a configuration, the opening groove 12 is expanded to fit the shaft portion of the leader pin into the internal space 11, and the shaft portion of the leader pin is clamped with an elastic force together with the magnetic tape wound around the shaft portion. Thus, the leader pin is fixedly held on one end of the magnetic tape.

JP 2000-11596 A

  As described above, the clamp member 10 is made of an injection molded body of a synthetic resin material. However, the conventional clamp member 10 has a gate trace G in the region facing the formation region of the opening groove 12 on the C-shaped end surface. Is formed. Therefore, in the region opposite to the region where the opening groove 12 is formed, the axial direction of the clamp member 10 is as shown by the arrow F in the flow orientation of the molten resin injected from the gate as schematically shown in FIGS. As a result, the constituent molecules of the synthetic resin material are axially oriented in the region.

  However, in this case, as schematically shown in FIGS. 12 and 13, when the leader pin 15 is assembled or after the assembly, the clamp member 10 is cracked by the bending load W, and the clamp member 10 is expected. In some cases, the clamping force cannot be obtained. For this reason, the leader pin is dropped from the magnetic tape and the magnetic tape cannot be properly drawn out, which may impair the reliability of the magnetic tape cartridge.

  This is because the largest bending load is applied to the region opposite to the formation region of the opening groove 12 by the opening groove 12 being expanded when the clamp member 10 and the leader pin 15 are assembled. The synthetic resin material constituting the region is oriented along the axial direction of the clamp member, so that it is considered that the cause is that the yield strength against the bending load is reduced.

  In addition, since the gate is provided in the region where the maximum load is applied as described above, a crack starting from the gate position is likely to occur due to the residual stress of the resin generated around the gate, the weld line, etc. It is also possible that

  The present invention has been made in view of the above-described problems, and provides a magnetic tape cartridge capable of enhancing the durability of a clamp member for fixing and holding a leader pin to one end of a magnetic tape to ensure reliability, and a method for manufacturing the same. Let it be an issue.

  In solving the above problems, the magnetic tape cartridge of the present invention is formed with an internal space for housing the shaft portion of the leader pin and a width dimension smaller than the shaft diameter of the shaft portion of the leader pin. On the other hand, the gate trace of the clamp member made of the synthetic resin material injection molded body having the opening groove communicating with the entire axial direction is opposed to the area facing the formation area of the opening groove across the internal space. The flow path of the synthetic resin material is formed at a position where the flow direction intersects, and at least in a region facing the formation region of the opening groove, a flow channel enlargement portion that locally increases the flow channel area is formed. It is characterized by being.

  Further, in the method for manufacturing the magnetic tape cartridge of the present invention, the flow passage enlarged portion of the synthetic resin material is formed in a region opposed to the formation region of the opening groove across the internal space, and the region in the opposed relationship is formed. The clamp member is formed by injecting a synthetic resin material in a direction crossing the clamp member.

  In the magnetic tape cartridge of the present invention configured as described above, the gate trace of the clamp member has a flow direction of the synthetic resin material with respect to a region opposed to the formation region of the opening groove across the internal space. Since it is formed at the intersecting position, the molecular orientation of the synthetic resin material in the opposite region of the opening groove intersects with the forming direction of the opening groove, thereby increasing the resistance against bending load in the region and cracking. Preventing the occurrence of

  In addition, by forming a flow channel enlargement part in a region opposite to the region where the opening groove is formed, the resin flow in the region is facilitated, and the resin molecules are orderly aligned in the flow direction to achieve the above-described cross relationship. Can be secured. Further, the increase in the thickness of the region can improve the strength, and the durability against bending load can be further enhanced.

  As the formation position of the gate mark that can satisfy the above-described configuration, the inner wall surface of the opening groove of the clamp member, the side peripheral surface in the vicinity of the opening groove of the clamping member, the one end surface in the vicinity of the opening groove of the clamping member, and the like are preferable. Since these positions are located in a region different from the region opposite to the region where the opening groove is formed, the applied external force is relatively small, and therefore, the generation of cracks starting from the gate position can be prevented.

  As described above, according to the magnetic tape cartridge of the present invention, the clamp member is located at the position where the flow direction of the synthetic resin material intersects the region facing the formation region of the opening groove across the internal space. Therefore, the durability of the clamp member due to the bending load during or after the assembly of the clamp member with respect to the leader pin can be enhanced, and the reliability of the magnetic tape cartridge can be ensured.

  Moreover, according to the method for manufacturing a magnetic tape cartridge of the present invention, a clamp member having excellent mechanical strength can be manufactured with high productivity.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, the overall configuration of the magnetic tape cartridge 20 of the present embodiment will be described with reference to FIGS.

  The cartridge main body 21 of the magnetic tape cartridge 20 is configured by connecting an upper half 21 a and a lower half 21 b with four screw members 43. A single reel 23 around which a magnetic tape 22 is wound is accommodated inside the cartridge body 21. The reel 23 is configured by integrating an upper reel flange 44 and a lower reel flange 45 integral with the hub 51 by ultrasonic bonding.

  A reel rotation driving gear 25 that engages with the spindle of the tape drive device is formed in an annular shape on the lower surface of the reel 23, and is exposed to the outside through an opening 24 provided in the center of the lower half 21b. (FIG. 2). An annular magnet plate 49 that is magnetically attracted to the spindle is attached to the inner side of the reel rotation drive gear 25.

  A spider 46, a reel lock member 47, and a reel lock spring 48 are provided between the upper half 21 a and the reel 23.

  The spider 46 has a substantially triangular shape, and leg portions 46a projecting downward at the respective apexes thereof are respectively inserted into insertion holes 51b formed in the hub 51. A circular slidable contact portion 46b is provided on the upper surface of the spider 46, and a substantially spherical protrusion (not shown) provided at the center of the lower surface of the reel lock member 47 contacts the slidable contact portion 46b. Thus, the reel lock member 47 is rotatably supported.

  The reel lock member 47 receives an urging force of a reel lock spring 48 formed of a coil spring, and a gear portion 47a formed in an annular shape on the bottom surface thereof meshes with a plurality of arc-shaped gear portions 51a erected inside the hub 51. By doing so, the operation of restricting the rotation of the reel 23 when the magnetic tape cartridge 20 is not used is performed.

  When the magnetic tape cartridge 20 is used, a drive release spindle of a tape drive device (not shown) presses the spider 46 from below and moves the reel lock member 47 upward against the urging force of the reel lock spring 48. As a result, the meshing between the gear portion 47a of the reel lock member 47 and the gear portion 51a of the hub 51 is released, and the reel 23 is rotatable.

  On the other hand, an opening 27 for pulling out one end of the magnetic tape 22 to the outside is provided on one side wall 26 of the cartridge body 21. Inside the side wall 26, a wall portion 39 is formed at a predetermined distance from the side wall 26, and the side wall 26 and the wall portion 39 guide the movement of the openable slide door 29 of the opening 27. A guide groove 41 is formed. The guide groove 41 is configured not only in the lower half 21b side but also in the same form on the upper half 21a side, not shown.

  An engagement portion 29 a is provided at one side edge of the slide door 29 to allow the tape transport mechanism of the tape drive device to chuck and open the slide door 29. In the guide groove 41, a W-shaped torsion spring 57 for biasing the slide door 29 to the closed position is accommodated.

  In addition, a safety tab 53 for preventing accidental erasure of information recorded on the magnetic tape 22 is slidably attached to the other side wall of the cartridge main body 21, and information recorded on the magnetic tape 22 can be stored. A non-contact readable / writable IC substrate 54 is inclined.

  Further, a display 60 indicating the insertion direction of the cartridge with respect to the tape drive device is recessed in the upper front side of the upper half 21a.

  A metal leader pin 31 is fixed to one end of the magnetic tape 22. The leader pin 31 can be attached to and detached from the pin holding portion 30 provided on the inner side of the opening 27. The pin holding portion 30 is configured by an elastic holder 33 that is mounted symmetrically with respect to both the upper wall inner surface (upper half 21a inner surface) and the bottom wall inner surface (lower half 21b inner surface) of the cartridge body 21. The upper and lower ends of the leader pin 31 are supported by these elastic holders 33.

  4A and 4B, the leader pin 31 is fixedly held on one end of the magnetic tape 22 via a clamp member 52. As shown in FIG. The clamp member 52 is fitted to the shaft portion 32 of the leader pin 31 around which one end of the magnetic tape 22 is wound, and the upper and lower end surfaces 52a have a substantially C shape.

  The length (height) of the clamp member 52 in the axial direction is formed slightly shorter than the distance between the pair of flange portions 34 formed to protrude from the leader pin shaft portion 32, and is incorporated between the pair of flange portions 34. It is supposed to be.

  The clamp member 52 has an internal space 55 for housing the leader pin shaft portion 32 in the shaft center portion. The internal space 55 is formed to be slightly narrower than the leader pin shaft portion 32, and is configured to clamp the leader pin shaft portion 32 with a predetermined clamping pressure after assembly.

  On the other hand, an opening groove 56 is formed in the side periphery of the clamp member 52 along the axial direction thereof. The opening groove 56 is formed with a width dimension smaller than the shaft diameter of the leader pin shaft portion 32, and communicates with the internal space 55 over the entire region in the axial direction. Accordingly, when the clamp member 52 is assembled to the leader pin shaft portion 32, the opening groove 56 is pushed and widened so that the leader pin shaft portion 32 is incorporated into the internal space 55. After the assembly, the elastic force of the clamp member 52 is obtained. Thus, the leader pin shaft portion 32 is clamped.

  The clamp member 52 configured as described above is an injection-molded body made of a synthetic resin material such as polycarbonate. In the present invention, the gate trace of the clamp member 52 flows to the region 58 (hereinafter referred to as “opening groove facing region”) facing the forming region of the opening groove 56 with the internal space 55 interposed therebetween. It is formed at a position where the directions intersect. Hereinafter, embodiments of the gate trace formation position that satisfies such conditions will be described separately.

(First embodiment)
5A and 5B show the configuration of the clamp member 52A according to the first embodiment of the present invention. In the figure, portions corresponding to those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.
Here, FIG. 5A is an overall perspective view of the clamp member 52A on the opening groove 56 forming surface side, and FIG. 5B is a rear view (surface opposite to the opening groove 56 forming surface) of the clamp member 52A.

  In the clamp member 52 </ b> A of the present embodiment, the gate mark G <b> 1 is formed on the inner wall surface of the opening groove 56.

  In particular, in the present embodiment, the gate mark G1 is formed on the inner wall surface of the opening groove 56 and at the center position in the height direction of the clamp member 52A. However, the present invention is not limited to this, for example, the upper end surface 52a of the clamp member 52A or A position close to the lower end surface 52b may be used. For example, a submarine gate method is suitable as a gate method for forming the clamp member 52A having the configuration as in this example.

  Next, on the inner surface side of the internal space 55, a plurality of flat surfaces 55a, 55b, and 55c are formed along the axial direction of the clamp member 52A. Among these, the flat surface 55a is formed at a position facing the formation region of the opening groove 56, thereby constituting the “flow channel expanding portion” according to the present invention. On the other hand, the flat surfaces 55b and 55c are formed at positions facing each other, but may be omitted if necessary. These flat surfaces 55a to 55c are in contact with the leader pin shaft portion 32 housed in the internal space 55, and ensure a stable clamping action of the leader pin.

  In the clamp member 52A configured as described above, the synthetic resin material radially injected from the formation position of the gate mark G1 flows and is molded in the direction indicated by the arrow F1. Accordingly, as shown in FIG. 5B, the flow orientation of the resin can be given in the direction intersecting the opening groove facing area 58 (area between the two broken lines indicating the opening groove 56), and therefore the opening groove facing area 58. It becomes possible to give high resistance to the bending load applied to.

  Moreover, since the flat surfaces 55a-55c are provided in the inner surface part of the internal space 55, and the flow path expansion part which makes the flow path area of a synthetic resin material large locally is formed, these flat surfaces 55a-55c. The flow of the synthetic resin material injected from the gate position (G1) provided on the upstream side can be facilitated. As a result, the resin molecules can be ordered in the flow direction in the opening groove facing region 58 and the above-described crossing relationship can be ensured. Further, the increase in the thickness of the region can improve the strength, and the durability against bending load can be further enhanced.

  Therefore, according to the present embodiment, when the clamp member 52A is assembled to the shaft portion 32 of the leader pin 31, cracks due to a bending load in the opening groove facing region 58 generated along with the opening and spreading action of the opening groove 56 are generated. Generation | occurrence | production can be suppressed and durability of 52 A of clamp members can be improved. Thereby, separation of the magnetic tape 22 and the leader pin 31 can be avoided, an appropriate drawing operation of the magnetic tape 22 can be ensured, and the reliability of the magnetic tape cartridge 20 can be maintained.

  Further, since the gate position is formed in a region where the external force is not easily applied to the clamp member 52A, it is possible to avoid the occurrence of cracks due to the residual stress at the time of molding around the gate portion, and to contribute to the improvement of the durability of the clamp member 52A. .

(Second Embodiment)
6A and 6B show the configuration of the clamp member 52B according to the second embodiment of the present invention. In the figure, portions corresponding to those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.
Here, FIG. 6A is an overall perspective view of the clamping member 52B on the opening groove 56 forming surface side, and FIG. 6B is a rear view (surface opposite to the opening groove 56 forming surface) of the clamping member 52B.

  In the clamp member 52B of the present embodiment, the gate mark G2 is formed on the side peripheral surface near the opening groove 56 of the clamp member 52B.

  In particular, in the present embodiment, the gate trace G2 is formed on the side peripheral surface in the vicinity of the opening groove 56 and in the center in the height direction of the clamp member 52B. However, the present invention is not limited to this, and the upper and lower end surfaces 52a of the clamp member 52B. , 52b, etc. For example, a submarine gate system is suitable as a gate system for forming the clamp member 52B having the configuration as in this example.

  Next, on the inner surface side of the internal space 55, a plurality of flat surfaces 55a, 55b, and 55c are formed along the axial direction of the clamp member 52B. Among these, the flat surface 55a is formed at a position facing the formation region of the opening groove 56, thereby constituting the “flow channel expanding portion” according to the present invention. On the other hand, the flat surfaces 55b and 55c are formed at positions facing each other, but may be omitted if necessary. These flat surfaces 55a to 55c are in contact with the leader pin shaft portion 32 housed in the internal space 55, and ensure a stable clamping action of the leader pin.

  In the clamp member 52B having the above-described configuration, the synthetic resin material radially injected from the formation position of the gate mark G2 flows and is molded in the direction indicated by the arrow F2. Accordingly, as shown in FIG. 6B, the flow orientation of the resin can be given in the direction intersecting the opening groove facing region (the region between the two broken lines indicating the opening groove 56) 58. It becomes possible to give high resistance to the bending load applied to.

  Moreover, since the flat surfaces 55a-55c are provided in the inner surface part of the internal space 55, and the flow path expansion part which makes the flow path area of a synthetic resin material large locally is formed, these flat surfaces 55a-55c. The flow of the synthetic resin material injected from the gate position (G2) provided on the upstream side can be facilitated. As a result, the resin molecules can be ordered in the flow direction in the opening groove facing region 58 and the above-described crossing relationship can be ensured. Further, the increase in the thickness of the region can improve the strength, and the durability against bending load can be further enhanced.

  Therefore, according to the present embodiment, when the clamp member 52B is assembled to the shaft portion 32 of the leader pin 31, cracks due to the bending load in the opening groove facing region 58 that are generated along with the expanding action of the opening groove 56 are generated. Generation | occurrence | production can be suppressed and durability of the clamp member 52B can be improved. Thereby, separation of the magnetic tape 22 and the leader pin 31 can be avoided, an appropriate drawing operation of the magnetic tape 22 can be ensured, and the reliability of the magnetic tape cartridge 20 can be maintained.

  Further, since the gate position is formed in a region where the external force is not easily applied to the clamp member 52B, it is possible to avoid the occurrence of cracks due to the residual stress at the time of molding around the gate portion, and to contribute to the improvement of the durability of the clamp member 52B. .

(Third embodiment)
7A and 7B show the configuration of a clamp member 52C according to the third embodiment of the present invention. In the figure, portions corresponding to those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.
7A is a perspective view of the clamp member 52C as viewed from the upper end surface 52a side, and FIG. 7B is a rear view of the clamp member 52C (surface opposite to the surface on which the opening groove 56 is formed).

  In the clamp member 52C of the present embodiment, the gate mark G3 is formed on the upper end surface 52a in the vicinity of the opening groove 56 of the clamp member 52C.

  In particular, as shown in FIG. 8, the gate mark G3 has a straight line passing through the center O of the internal space 55 and the center of the width of the opening groove 56 as the Y axis, and a straight line passing through the center O and perpendicular to the Y axis as the X axis. It is preferable to form it on the end face 52a corresponding to the first quadrant S1 or the second quadrant S2 in the orthogonal coordinate system. In other regions, the crossing angle of the resin flow orientation with respect to the opening groove forming region 58 becomes small, and the possibility that a crack starting from the gate position is generated by the bending load applied to the clamp member 52C is increased.

  The formation surface of the gate mark G3 is not limited to the upper end surface 52a of the clamp member 52C, and may be the lower end surface thereof. In addition, as a gate system for shaping | molding the clamp member 52C of a structure like this example, a pin gate system is suitable, for example.

  Next, a plurality of flat surfaces 55a, 55b, and 55c are formed on the inner surface side of the internal space 55 along the axial direction of the clamp member 52C. Among these, the flat surface 55a is formed at a position facing the formation region of the opening groove 56, thereby constituting the “flow channel expanding portion” according to the present invention. On the other hand, the flat surfaces 55b and 55c are formed at positions facing each other, but may be omitted if necessary. These flat surfaces 55a to 55c are in contact with the leader pin shaft portion 32 housed in the internal space 55, and ensure a stable clamping action of the leader pin.

  In the clamp member 52C having the above-described configuration, the synthetic resin material radially injected from the formation position of the gate mark G3 flows and is molded in the direction indicated by the arrow F3. Accordingly, as shown in FIG. 7B, the flow orientation of the resin can be given in a direction intersecting the opening groove facing area 58 (area between the two broken lines indicating the opening groove 56). Thus, it becomes possible to provide high resistance to the bending load applied to the clamp member 52C.

  Moreover, since the flat surfaces 55a-55c are provided in the inner surface part of the internal space 55, and the flow path expansion part which makes the flow path area of a synthetic resin material large locally is formed, these flat surfaces 55a-55c. The flow of the synthetic resin material injected from the gate position (G3) provided on the upstream side can be facilitated. As a result, the resin molecules can be ordered in the flow direction in the opening groove facing region 58 and the above-described crossing relationship can be ensured. Further, the increase in the thickness of the region can improve the strength, and the durability against bending load can be further enhanced.

  Therefore, according to the present embodiment, when the clamp member 52C is assembled to the shaft portion 32 of the leader pin 31, cracks due to the bending load in the opening groove facing region 58 that are generated along with the expanding action of the opening groove 56 are generated. Generation | occurrence | production can be suppressed and durability of 52 C of clamp members can be improved. Thereby, separation of the magnetic tape 22 and the leader pin 31 can be avoided, an appropriate drawing operation of the magnetic tape 22 can be ensured, and the reliability of the magnetic tape cartridge 20 can be maintained.

  Further, since the gate position is formed in the region where the external force is not easily applied to the clamp member 52B, it is possible to avoid the occurrence of cracks due to the residual stress at the time of molding around the gate portion, and to contribute to the improvement of the durability of the clamp member 52C. .

(Fourth embodiment)
9A and 9B show a fourth embodiment of the present invention. In the figure, portions corresponding to those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof is omitted.
Here, FIG. 9A is a front view of the clamp member 52D viewed from the opening groove 56 side, and FIG. 9B is a bottom view thereof.

  In the clamp member 52D of the present embodiment, the gate mark G4 is formed in the vicinity of the opening groove 56 of the lower end surface 52b of the clamp member 52D. The formation region of the gate mark G4 on the lower end surface 52b of the clamp member 52D is the same as that in the third embodiment.

  The gate mark G4 is formed in a recess 59 in which a partial region facing the opening groove 56 of the lower end surface 52b of the clamp member 52D is lowered by one step. This recess corresponds to a portion where the gate bush is disposed during molding.

  Further, on the inner wall surface forming the internal space 55 of the clamp member 52D, the position facing the opening groove facing region 58 is a flat surface 55a. Thereby, the “flow channel expanding portion” of the present invention is configured, and the mechanical strength of the opening groove facing region 58 is improved. Further, in the other two regions sandwiching the leader pin shaft portion, projecting portions 55b 'and 55c' are formed in the axial direction so as to stabilize the clamping action. The tips of the protrusions 55b 'and 55c' are flat surfaces.

  Also by the clamp member 52D of the present embodiment configured as described above, the same effects as those of the above-described third embodiment can be obtained. In particular, according to the present embodiment, the post-processing (burr removal or the like) of the gate trace G4 can be made unnecessary by forming the recess 59. The configuration in which the gate is disposed in the recess 59 provided on the outer surface of the clamp member in this manner can be similarly applied to the first and second embodiments described above. Further, when the gate is arranged not only on the outer surface of the clamp member but also on the inner surface of the clamp member (the inner surface of the inner space 55), the above recess is formed in the same manner, and the gate is arranged there. Can do. Furthermore, the form of the recess 59 is not limited to this example, and for example, a form having both side walls as shown in FIG. 10 is also included.

  Also, in the magnetic tape cartridge manufacturing process, there is a process of automatically assembling the clamp member to the leader pin, but the recess 59 can be used for positioning the clamp member, thereby realizing an appropriate clamp member assembling process. It becomes possible.

  In this example, the gate mark G4 is formed on the lower end surface 52b of the clamp member 52D. Of course, the same effect can be obtained by forming the gate mark G4 on the upper end surface 52a.

  As described above, according to the present embodiment, the durability of the clamp member 52 (52A to 52D) can be greatly improved as compared with the prior art, so that the generation of cracks during assembly to the leader pin 31 is prevented. In addition, after assembly, the desired clamping force can be maintained over a long period of time, whereby the reliability of the magnetic tape cartridge 20 can be ensured.

  In addition, the range of molding conditions of the clamp member 52 is widened, and productivity can be improved. In other words, it was necessary to control the molding conditions (for example, mold temperature and resin temperature) very strictly to minimize the residual stress at the time of molding and to suppress the thermal degradation of the resin. By changing the gate position to a region where it hardly acts, the effects of residual stress and thermal degradation of the resin are reduced, which makes it possible to increase the range of molding conditions and greatly contribute to productivity improvement and yield improvement. Will be able to.

  As mentioned above, although each embodiment of this invention was described, of course, this invention is not limited to these, A various deformation | transformation is possible based on the technical idea of this invention.

  For example, in each of the above embodiments, the gate position of the clamp member is formed on the side circumferential surface or one end surface in the vicinity of the opening groove, but not limited to this, the opening groove facing region of the clamp member and the synthetic resin material Any position that intersects the flow direction may be used. For example, the same effect as described above can be obtained even if the gate is arranged on the inner wall surface of the internal space 55 near the opening groove 56.

1 is a perspective view showing an entire magnetic tape cartridge 20 according to an embodiment of the present invention. 3 is a perspective view showing the back side of the magnetic tape cartridge 20. FIG. 3 is an exploded perspective view of the magnetic tape cartridge 20. FIG. FIG. 3 is a perspective view showing the configuration of a leader pin 31 and a clamp member 52 in the magnetic tape cartridge 20, wherein A shows a state before assembly and B shows a state after assembly. It is a figure which shows the structure of 52 A of clamp members by the 1st Embodiment of this invention, A is a whole perspective view, B is the rear view seen from the opening groove opposing area | region 58 side. It is a figure which shows the structure of the clamp member 52B by the 2nd Embodiment of this invention, A is a whole perspective view, B is the rear view seen from the opening groove opposing area | region 58 side. It is a figure which shows the structure of the clamp member 52C by the 3rd Embodiment of this invention, A is the perspective view seen from the upper end surface side, B is the rear view seen from the opening groove opposing area | region 58 side. It is a figure explaining the formation position range of the gate mark G3 in the clamp member 52C. It is a figure which shows the structure of clamp member 52D by the 4th Embodiment of this invention, A is a front view, B is a bottom view. It is a perspective view of the principal part which shows the structure of the clamp member in the conventional magnetic tape cartridge. It is a figure explaining the gate position of the conventional clamp member, and its resin flow orientation. It is a side view which shows typically the generation | occurrence | production state of the crack which generate | occur | produces at the time of the assembly | attachment of the conventional clamp member. It is a top view which shows typically the generation | occurrence | production state of the crack which generate | occur | produces at the time of the assembly | attachment of the conventional clamp member.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 20 ... Magnetic tape cartridge, 21 ... Cartridge main body, 22 ... Magnetic tape, 23 ... Reel, 27 ... Opening part, 31 ... Leader pin, 32 ... Shaft part, 52, 52A-52D ... Clamp member, 55 ... Internal space, 55a to 55c: flat surface (flow path expanding portion), 56: opening groove, 58: opening groove facing region, F1 to F3: flow direction, G1 to G4: gate trace.

Claims (8)

A reel on which a magnetic tape is wound, a cartridge main body that rotatably stores the reel, a leader pin that is attached to one end of the magnetic tape and for pulling out the magnetic tape, and the leader pin is fixed to one end of the magnetic tape. A clamp member for holding, the clamp member is formed with an internal space for accommodating the shaft portion of the leader pin, and a width dimension smaller than the shaft diameter of the shaft portion, and the entire axial direction with respect to the internal space. In a magnetic tape cartridge made of an injection molded body of a synthetic resin material having an open groove communicating with
The gate mark of the clamp member is formed at a position where the flow direction of the synthetic resin material intersects with a region facing the formation region of the opening groove across the internal space,
A magnetic tape cartridge characterized in that a flow path expanding portion that locally increases a flow path area is formed at least in a region facing the formation region of the opening groove. The magnetic tape cartridge according to claim 1, wherein the gate mark is formed on an inner wall surface of the opening groove of the clamp member. The magnetic tape cartridge according to claim 1, wherein the gate mark is formed on a side peripheral surface of the clamp member in the vicinity of the opening groove. The magnetic tape cartridge according to claim 1, wherein the gate mark is formed on one end surface of the clamp member in the vicinity of the opening groove. The flow passage expanding portion is formed at a plurality of locations in the flow direction of the synthetic resin material, and the gate mark is formed on the most upstream side of the plurality of flow passage expanding portions. Item 2. The magnetic tape cartridge according to Item 1. 2. The magnetic tape cartridge according to claim 1, wherein a contact surface of the inner space with respect to the shaft portion of the leader pin is a flat surface, and the flat surface forms the flow path expanding portion. The magnetic tape cartridge according to claim 1, wherein the gate mark is formed in a recess provided on a surface of the clamp member. A reel on which a magnetic tape is wound, a cartridge main body that rotatably stores the reel, a leader pin that is attached to one end of the magnetic tape and for pulling out the magnetic tape, and the leader pin is fixed to one end of the magnetic tape. A clamp member for holding, the clamp member is formed with an internal space for accommodating the shaft portion of the leader pin, and a width dimension smaller than the shaft diameter of the shaft portion, and the entire axial direction with respect to the internal space. In a manufacturing method of a magnetic tape cartridge comprising an injection molded body of a synthetic resin material having an open groove communicating over
At least forming a flow path expanding portion of the synthetic resin material in a region facing the formation region of the opening groove across the internal space,
A method of manufacturing a magnetic tape cartridge, comprising: injecting the synthetic resin material in a direction intersecting a region opposite to a region where the opening groove is formed, and molding the clamp member.

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